Memory devices can be categorized in two broad areas: volatile and non-volatile. Volatile memory devices require power to maintain data, while non volatile memories are capable of maintaining data in the absence of a power supply. An example of a non-volatile memory is the flash memory that stores information in a semiconductor device without the need for power being supplied to the semiconductor device in order to maintain the information in the semiconductor device.
Flash memory may be built using either NOR or NAND devices. NAND flash may be either of single-level cell (SLC) or multiple-level cell (MLC) configuration. MLC NAND flash allows for a higher density memory device in comparison to SLC NAND flash because it allows the storage of two or more data bits in each memory cell.